The present invention relates to a lock, particularly a mortise lock, with bolt and preferably catch and a step-up lever which is provided with a closure-engagement opening and acts on the bolt for the moving forward and back of the bolt while obtaining a lengthening of the closing stroke, and furthermore with another lever which can be lifted away by a closure bit against spring action.
A lock of the type in question is known from Federal Republic of Germany Utility Model 16 41 147, in which the single-arm step-up lever which is mounted below the closure-bit insertion opening is in pin/slot engagement with the bolt at its free end. In the region of the closure-bit insertion opening, the step-up lever forms an opening which is provided with a closure engagement opening which is directed radially to the bolt. A turn pin extends adjacent to the closure-engagement opening. This pin cooperates with the turn recesses of tumblers mounted on the lock-housing side. Such a lock is not suitable for closure cylinders developed as profiled cylinders. Furthermore, push-back forces exerted on the bolt upon an attempt at breaking in act on the step-up lever, doing so also in stepped-up manner, together with poor security against breaking-in.
From Federal Republic of Germany OS 26 42 367, there is also known a lock the step-up lever of which is also in pin/slot engagement with the bolt. The step-up lever itself does not form a closure engagement opening, but it is acted on on its corresponding rear edge only upon the advancing of the bolt. Upon backward movement by means of the closure member of the profiled cylinder, the cylinder acts on an angle arm of a slide guided in the bolt. This development requires a large number of parts and leads to an increased expense in manufacture.